1. Field of the Invention
The present invention relates to a method of manufacturing a voice coil, and more particularly, to a method of manufacturing a voice coil in which a coil pattern is formed on a wafer level package.
2. Discussion of Related Art
Camera modules are divided into a voice coil motor (VCM) type, an encoder type, and a piezo type, and the VCM type module is being mostly applied in terms of cost-effectiveness. In the VCM among them, force which is proportional to the magnetic flux density of a permanent magnet magnetic field and current which flows through a coil is generated in a direction perpendicular to the magnetic field and the current to move a lens to an optimum position.
Meanwhile, when the VCM vertically moves along a cam structure by the rotation of an actuator, the separation of the lens from a focusing state occurs due to lens tilt, backlash, external shock, vibration, or the like. Therefore, in order to stably operate without vibration during the vertical movement, a spring having a preload for an autofocusing (AF) module is required. Using the spring, the lens is precisely guided and supported, the impact force that occurs when using a mobile phone is cushioned, and thus the lens is protected.
However, when the spring is permanently deformed due to shocks or the like, a driving tilt occurs and thus driving separation occurs in a diagonal direction rather than the vertical direction during the vertical movement. Accordingly, since the variation of images is generated left and right or up and down, it is difficult to obtain precise images.
Further, a coil applied to the VCM depends on maximum flux density. Accordingly, when the coil exceeds the maximum flux density, the coil reaches a magnetic saturation state, loses magnetism, and thus can be a simple wire. Therefore, when high maximum flux density is required, a volume to such a degree that the magnetic saturation of the coil does not occur is required.
Meanwhile, in a case of a coil winding applied to an optic image stabilizer (OIS) actuator, which is used as a shake compensator, or the like, a thickness thereof is large and a manufacturing method is limited, and thus it is difficult to implement a fine critical dimension. Further, it is disadvantageous that the efficiency of a degree of integration is decreased resulting from the above-described problems. When the corresponding coil winding is implemented to a device, it is advantageous that the volume of the camera module can be reduced. Specifically, in the VCM having a spring type, since the influence on the permanent deformation of the spring can be minimized, it is advantageous that reliability can be increased.
Therefore, it is necessary to implement the fine critical dimension by increasing the thickness of the coil winding applied to the actuator or the like. However, there is a limit to a conventional coil winding manufacturing method having a redistributed layer (RDL) type.